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Genes controlling the transition to flowering have been studied in several species, including Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa), but have not yet received much attention in legumes. Here, we describe a new allelic series of late-flowering, photoperiod-insensitive mutants in the pea (Pisum sativum) LATE BLOOMER1 (LATE1) gene and show that LATE1 is an ortholog of Arabidopsis GIGANTEA. Mutants display defects in phytochrome B-dependent deetiolation under red light and in the diurnal regulation of pea homologs of several Arabidopsis circadian clock genes, including TIMING OF CAB1, EARLY FLOWERING4, and CIRCADIAN CLOCK ASSOCIATED1/LATE ELONGATED HYPOCOTYL. LATE1 itself shows strongly rhythmic expression with a small but distinct acute peak following dark-to-light transfer. Mutations in LATE1 prevent the induction of a FLOWERING LOCUS T (FT) homolog FTL in long days but cause only minor alteration to the rhythmic expression pattern of the only known group Ia CONSTANS homolog COLa. The late-flowering phenotype of late1 mutants can be completely rescued by grafting to the wild type, but this rescue is not associated with a significant increase in FTL transcript level in shoot apices. Genetic interactions of late1 with the photoperiod-insensitive, early-flowering sterile nodes (sn) mutant and impairment of the LATE1 diurnal expression rhythm in sn plants suggest that SN may also affect the circadian clock. These results show that several functions of Arabidopsis GIGANTEA are conserved in its pea ortholog and demonstrate that genetic pathways for photoperiodic flowering are likely to be conserved between these two species. They also suggest that in addition to its role in the floral transition, LATE1 also acts throughout reproductive development.

We describe the design and commissioning of the photon tagging beamline installed in experimental Hall B at the Thomas Jefferson National Accelerator Facility (JLab). This system can tag photon energies over a range from 20% to 95% of the incident electron energy, and is capable of operation with beam energies up to 6.1 GeV. A single dipole magnet is combined with a hodoscope containing two planar arrays of plastic scintillators to detect energy-degraded electrons from a thin bremsstrahlung radiator. The first layer of 384 partially overlapping small scintillators provides photon energy resolution, while the second layer of 61 larger scintillators provides the timing resolution necessary to form a coincidence with the corresponding nuclear interaction triggered by the tagged photon. The definitions of overlap channels in the first counter plane and of geometric correlation between the two planes are determined using digitized time information from the individual counters. Auxiliary beamline devices are briefly described, and performance results to date under real operating conditions are presented. The entire photon-tagging system has met or exceeded its design goals.

Cross-section measurements of a collinear configuration, the space-star and the coplanar-star configurations in nd breakup at E n = 13.0 MeV are reported. The present measurements for the collinear configuration are in good agreement with pd and nd data. Our coplanar-star data are consistent with theoretical predictions and resolve the reported problem with this configuration. The previously observed large discrepancy between theory and nd cross-section data for the space-star configuration is confirmed in the present work.

We report on the formation of carbon nanotubes and encapsulated metal nanoparticles produced during the electric arc discharge between a graphite cathode and a graphitic anode containing different stoichiometric mixtures of Ni, Y and B. Using these mixtures it can be shown that Ni plays a catalytic role in the formation of single-walled nanotubes (SWTs). However, the active catalytic amount of Ni used in the experiment can be increased by additionally introducing certain other metals in the anode. Their melting point, vapour pressure and their affinity towards carbon seem to have an important influence on the amount of SWTs produced, as well as on the amount of metal particles encapsulated in multi-walled nanotubes (MWTs) and graphitic polyhedral nanoparticles (GNPs).

Results of our recent kinematically complete cross-section measurements of the space-star and coplanar-star configurations in n-d breakup at 13.0 MeV are reported. The experimental setup and details of the analysis are described. The new data for the space-star configuration are in good agreement with previous n-d data but differ significantly from both “exact” n-d calculations and p-d data. In constrast, the new coplanar-star data are in fair agreement with the calculations but are in gross disagreement with previous n-d data. The implications of these data for three-nucleon forces are discussed.

We report on some of the conditions during sublimation which promote single-shell carbon nanotube formation. Using as a catlyst a mixture of two metals (Co and Pt) in the anode, we observe a higher density of single-shell carbon nanotubes than that found with cobalt alone. Using other mixtures (Co and Fe), the nanotube yield is always lower, and their formation is even hindered (Co and Ru). First attempts of vacuum annealing at high temperature on samples containing cobalt-catalyzed single-shell carbon nanotubes suggest that this might be a good way to eliminate the catalyst particles. We present high-resolution transmission electron microscopy images of samples obtained by such procedures.

The different contributions which participate to the shift and broadening of an intramolecular mode in the plastic phase of C 60 are recalled. Especially, using a rotational diffusion model, we calculate the expected step of the linewidth of the A g and H g Raman modes related to the slowing down of the reorientational process at the order-disorder phase transition. For H g modes a value of the order of 2 cm -1 is calculated. On the other hand, we have performed a detailed analysis of the temperature dependence of the Raman spectrum of C 60 . We state that the slowing down of the reorientational process cannot explain alone the changes with temperature of the profile of the H g mode. We show that the room temperature spectrum of the 1426 cm -1 and 1575 cm -1 tangential H g modes results from the overlap of several components and changes with temperature of the profile of the H g mode are mainly related to an opposite temperature dependence of the intensity of these components and not to a dramatic narrowing of these modes.

We report the measurement of the 13C NMR frequency in K3C60 under pressure. Comparing pressure dependences of the hyperfine spin lattice relaxation rate and of the resonance frequency provides the first determination of the 13C Knight shift ((61 ± 4) p.p.m.) and of the chemical shift of the C603- molecule (125 p.m.m./TMS). NMR data under pressure can be undestood with a weak-Coulomb-interaction model.

The present paper identifies unique symmetry properties of the [ital [rvec d]]+[ital d][r arrow][ital d]+[ital p]+[ital n] breakup reaction that make it an excellent probe for studying charge-symmetry breaking. Measurements were made for two configurations of the ejected particles in the breakup reaction to obtain values of the spin observables [ital A][sub [ital y]], [ital A][sub [ital y][ital y]], and [ital A][sub [ital z][ital z]]. These observables are compared for the mirror reactions [sup 2]H([ital [rvec d]],[ital dp])[ital n] and [sup 2]H([ital [rvec d]],[ital dn])[ital p] for the two angle pairs ([theta][sub [ital d]],[phi][sub [ital d]],[theta][sub [ital N]],[phi][sub [ital N]])=(17.0[degree],0[degree],17.0[degree],180[degree]) and (17.0[degree],0[degree],34.5[degree],180[degree]) for an incident deutron energy of 12 MeV. In addition, spin observables for the [sup 2]H([ital [rvec d]],[ital pn])[ital d] reaction at [theta][sub [ital p]]=[theta][sub [ital n]] and [phi][sub [ital p]]=[phi][sub [ital n]]+180[degree] are shown to provide a particularly good test of charge symmetry. Our [ital A][sub [ital y]], [ital A][sub [ital y][ital y]], and [ital A][sub [ital z][ital z]] data for the [sup 2]H([ital [rvec d]],[ital pn])[ital d] reaction at ([theta][sub [ital p]],[phi][sub [ital p]],[theta][sub [ital n]],[phi][sub [ital n]])=(17.0[degree],0[degree],17.0[degree],180[degree]) are used to illustrate this latter point. Of the ten charge-symmetric sets of observables measured, two were foundmore » to differ by 2.5 standard deviations.« less

We report interesting growth morphologies produced during the electric arc-discharge between a graphite cathode and a composite cobalt—graphite anode, which includes the abundant formation of single-shell carbon nanotubes of 1–2 nm diameter. As the pressure inside the chamber and the cobalt content of the electrode are varied these “carbon monotubes” are formed in bundles and in high density under certain conditions in the soot, webs and string-like structures that decorate the chamber and also on a collaret that forms around the conventional deposit containing multi-shell nanotubes. We present high-resolution transmission electron microscopy images of these structures and propose conditions that promote single-tube growth. We also notice, in some cases, novel formation of regularly spaced cobalt particles enclosed in graphitic capsules and surrounded by sheaths of soot.

We report the temperature and pressure dependence of 13 C nuclear spin-lattice relaxation time T 1 on K 3 C 60 in the normal state. Within the BCS electron-phonon pairing mechanism, we estimate the coupling strength and the relevant phonon mode involved to account for superconductivity.

Recent studies carried out on an organic superconductor, s-(BEDT-TTF) 2 I 3 , have shown the important role played by the 13 C isotope on the T c transition, when substitution is made on the central CC bond of the molecule. Simultaneously, Raman studies determined the frequency shifts observed in the CC stretching vibrations in the substituted samples and consequently, put in evidence the role of the intramolecular Ag vibrations. We have extended these studies to compounds of the new carbon family, the fullerenes, in which 82% of the carbon atoms were substituted with 13 C in C 60 . The superconducting transition measured on the same sample doped with potassium is lowered by 1.5 to 2K as compared to the standard material doped in similar conditions. In the Raman spectrum, the main Ag band measured at 1467 cm −1 in 12 C 60 is shifted to 1420 cm −1 in enriched 13 C 60 . Taking into account the ratio between the molecular weight of the enriched 13 C 60 and of the standard material, one predicts a theoretical value for this mode at 1418 cm −1 in the enriched sample. A preliminary analysis of the Raman spectrum will be presented.

We report the pressure and temperature dependences of 13C nuclear spin-lattice relaxation time T1 in the normal state of K3C60. From the 1/T1T temperature and pressure profiles, a Fermi-liquid theory is used to investigate the variation of the density of states and the amplitude of electron-electron interaction. Finally the results obtained are shown to support a pairing mechanism for superconductivity that would involve high-frequency modes.

EVOLVE simulation results of sputtering processes of Au films with 175 keV Ar ions are compared to available experimental results. Thicknesses of Au films are 23, 99 and 192 nm, which are small, comparable and large, respectively, compared to the range of Ar ions. As a result of dose-dependent analysis of Au films, a good agreement has been found if the displacement threshold energy of Au is assumed to be 12 eV. Reducing the surface binding energy of Au from 3.8 to 1.9 or even to 0.0 eV does not increase the sputtering yield as the elemental sputtering yield formula predicts. In fact, it has no significant effect at all on the sputtering yield if the elemental value, e.g. 36 eV, is used for the displacement threshold energy of Au. On the other hand, reducing the displacement threshold energy from 36 to 12 eV increases the sputtering yield by more than a factor of 2. The sputtering yield is expressed and discussed in terms of parametric relationships of the surface binding energy, displacement threshold energy, the film thickness and the fluence.

In this paper we review the results of a series of high-accuracy measurements on the neutron-deuteron (n-d) scattering system at incident neutron energies below 20 MeV. These measurements were designed to: 1) provide data of sufficient accuracy to be used to refine the parametrization of the nucleon-nucleon force, 2) to test the reaction dynamics in the “rigorous” calculations of three-nucleon (3N) breakup reactions, and 3) identify 3N scattering observables that are specifically sensitive to three-nucleon forces and/or off-shell effects. At TUNL we have measured vector analyzing powers Ay (θ) for n-d elastic scattering and the breakup reaction to an accuracy better than ± 0.005 and ± 0.020, respectively. Recent results on items 1) and 2) will be presented. Also, results of cross-section measurements for n-d and p-d breakup will be compared to a “rigorous” 3N calculation.

Recently we have made kinematically incomplete and complete measurements of the vector analyzing powers Ay(8) for the n-p final-state interaction (FSI) in the n-d breakup reaction at 12 MeV. The kinematitally incomplete (KI) experimental arrangement, measuring the momentum of one outgoing neutron and the energy of the proton, permitted us to measure several breakup processes simultaneously to a high statistical aCCUracy and was therefore favored over the kinematically complete (KC) arrangement in which both outgoing neutrons were detected. Consequently, the KC measurements were conducted by parasiting on the KI experiment by adding a pair of neutron detectors at forward angles to detect the Second outgoing neutron. The incentives for performing the measurements are multiple. The investigation of polarization effects in the n-d breakup processes Should provide unique information about various aspects of the nuclear force acting in this three-nucleon system. As is well known, the predictions of Ay(e) for n-d elastic scattering at low energies are strongly Sensitive to the inclusion of the Pand D-wave interactions, while in Contrast, the description of the dlfferentlal cross section ~(8) data displays only slight sensitivity to the Pand D-wave interactions.l, 2 Because of the sensitivities observed in the Ay(8) data for elastic Scattering, it is likely that the Ay(8) data for the breakup processes Wlll exhibit sensitlvlties to aspects of the nuclear force that are SUpPressed in the a(8) data. Also, effects due to the three-nucleon force and charge-symmetry breaking might be revealed in such polarization data. The technique employed in these measurements used the pulsed polar~zed beam facilities at Triangle University Nuclear Laboratory (TUNL). The experimental setup is shown in Fig. I. The polarized neutrons were ~roduced via the 2H(~,~) source reaction, using the neutrons emerging at 0o. The incident deuteron beam was pulsed to enable the use of

The interest in efficient intestinal delivery of health-promoting substances is increasing. However, the delivery of vulnerable substances such as enzymes requires specific attention. The transit through the stomach, where the pH is very low, can be detrimental to the enzymatic activity of the protein to be delivered. Here, we describe the microencapsulation of the model enzyme bile salt hydrolase (Bsh) using whey protein-gum arabic microencapsulates for food-grade and targeted enzyme delivery in the proximal region of the small intestine. Furthermore, the efficacy of enteric coating microencapsulates for site-specific enzyme delivery was compared in vitro with living Lactobacillus plantarum WCFS1 bacteria that endogenously produce the Bsh enzyme. Microencapsulates allowed highly effective protection of the enzyme under gastric conditions. Moreover, Bsh release under intestinal conditions appeared to be very efficient, although in the presence of pancreatin, the Bsh activity decreased in time due to proteolytic degradation. In comparison, L. plantarum appeared to be capable to withstand gastric conditions as well as pancreatin challenge. Delivery using encapsulates and live bacteria each have different (dis)advantages that are discussed. In conclusion, live bacteria and food-grade microencapsulates provide alternatives for dedicated enteric delivery of specific enzymes, and the choice of enzyme to be delivered may determine which mode of delivery is most suitable.

Cross-section measurements of six exit-channel configurations in nd breakup at 13.0 MeV are reported and compared to rigorous calculations. Except for the coplanar-star configuration, our data are consistent with previous data. The present data for all configurations, with the exception of the space star, are in good agreement with theoretical predictions. The previously observed large discrepancy between theory and data for the space-star configuration is confirmed in the present work. The inclusion of the Tucson-Melbourne 2π exchange three-nucleon force with a cutoff parameter that correctly binds the triton only changes the predicted cross section by 2%, a factor of 10 smaller than the amount needed to bring theory into agreement with data.

In this paper we present results for kinematically complete cross‐section measurements of the space‐star configuration in neutron‐deuteron breakup for an incident neutron energy of 13.0 MeV. These data are a subset of the results obtained in a recent experiment in which cross sections for 46 configurations were measured simultaneously. The experimental techniques are described. These new data are in good agreement with previous n‐d data but differ significantly from both rigorous n‐d calculations and proton‐deuteron breakup data.

Composite sheets and nanotubes of different morphologies containing carbon, boron, and nitrogen were grown in the electric arc discharge between graphite cathodes and amorphous boron-filled graphite anodes in a nitrogen atmosphere. Concentration profiles derived from electron energy-loss line spectra show that boron and nitrogen are correlated in a one-to-one ratio; core energy-loss fine structures reveal small differences compared to pure hexagonal boron nitride. Boron and carbon are anticorrelated, suggesting the substitution of boron and nitrogen into the carbon network. Results indicate that singlephaase CyBxNx as well as separated domains (nanosize) of boron nitride in carbon networks may exist.

We report the vapor phase growth of partially filled graphitic fibers, 20-30 nm in diameter and up to a micron in length, during a manganese catalyzed carbon electric arc discharge. The fiber morphology resembles that of catalytic chemical vapor deposited carbon filaments but the inside hollow contains intermittent precipitates and continuous filling of Mn that at times occupy g50% of fiber lengths. Transmission electron microscopy and electron energy loss line spectra show that the fillings form as solid cores and may correspond to pure metal.

We present NMR studies performed on AnC60 compounds, where A can be K, Rb, I2, O2 and n can be 1, 2, 3 and 6 depending on the system. Using high resolution NMR we have obtained information on the molecular dynamics and the electronic properties of these compounds. The shape of the 13 c spectra shows that intercalation of species like K and Rb, with n=6, totally block the molecular reorientation of the C60 at room temperature. On the contrary the effect of O2 is only partial while I2 does not hinder these reorientations. The 13C resonance positions are discussed in the light of existing theories concerning the NMR shifts in insulating and conducting media.

Raman spectra of both C60 and C70 fullerenes are at the present time well known and understood on both experimental and theoretical points of view. We have extended these studies to 13C substituted samples (82% substitution). As expected, an overall downshift of the Raman frequencies is observed, in good agreement with the values predicted from the total mass change of the molecules. In parallel studies carried out on the same samples intercalated with K at the superconducting level (K3C60), a significant shift in the Tc transition temperature has been measured. The isotope effect is therefore discussed in the framework of the BCS theory of superconductivity and compared to other published results.

We report the pressure dependence of 13C nuclear spin- lattice relaxation time T 1 in the normal state of K3C60. From the 1/T1T pressure profile, a Fermi liquid theory is used to investigate the variation of the density of states and the amplitude of electron-electron interaction. Finally, within a phonon-mediated pairing model for superconductivity, the combined pressure dependence of Tc and 1/T1T are shown to give strong support to a pairing mechanism via high energy modes ( < 1200 K).

Experimental methods to measure the vector analyzing powers over a broad range of kinematic configurations in the n-d breakup reaction have been developed at TUNL. These techniques employ the polarized beam facilities at TUNL and use the 2H( d , n )3He reaction as a source of low-energy polarized neutrons. Our methods permit measurements to a high statistical accuracy over a large fraction of three-nucleon phase space. The techniques are described and experimental spectra along with kinematic calculations are presented.

We report here interesting growth morphologies produced during the electric arc-discharge between a graphite cathode and different composite metal-graphite anodes: when the metal is pure cobalt powder, we obtain, under certain conditions of pressure and cobalt content in the electrode, many single-shell carbon nanotubes of 1–2 nm diameter which appear in the soot, webs, threads (in the reactor chamber) and also on a collaret that forms around the conventional deposit containing multi-shell nanotubes. When the metal is pure manganese powder, we obtain multi-layer hollow carbon fibers in the soot similar to the carbon fibers grown by catalytic chemical vapor deposition. Furthermore, many fibers have a good portion of the length filled with metal. We present here high-resolution transmission electron microscopy images of these structures.

Experimental and theoretical cross sections are presented for the /sup 6/Li(/sup 3/He,/sup 3/He/sup 3/He)/sup 3/H and /sup 6/Li(/sup 3/He,t/sup 3/He)/sup 3/He reactions for the symmetric angle pairs 20/sup 0/-20/sup 0/, 28.3/sup 0/-28.3/sup 0/, and 35/sup 0/-35/sup 0/. The theoretical cross sections are calculated in a three-body model where the trions (i.e., mass-3 nuclei) are treated as elementary particles with /sup 6/Li being a /sup 3/He-/sup 3/H bound state. The trion-trion interaction is represented by S wave separable potentials with the breakup cross sections calculated with the tree-body Haftel-Ebenhoeh code. the Coulomb interaction is taken into account by fitting the separable potential parameters to the trion-trion scattering data and is included approximately in the breakup code. The experimental cross sections are compared with both the plane-wave impulse approximation and the three-body model predictions. The plane-wave impulse approximation predicts both the shapes and magnitudes poorly (10 to 20 times experiment). Without Coulomb corrections the three-body model gives good agreement with experiment for the shapes of the spectra with the magnitudes generally being about 40% of experiment for /sup 6/Li(/sup 3/He,/sup 3/He/sup 3/He)/sup 3/H and about 80% for /sup 6/Li(/sup 3/He,t /sup 3/He)/sup 3/He. The Coulomb corrections improve the magnitudes predicted by themore » three-body model but not the shapes. It is observed that for these reactions S wave separable potentials describe the breakup data much better than they do the two-body trion-trion scattering data. This result should encourage further three-body treatment of these and similar reactions.« less

The cross section and the analyzing powers Ay, Axx, Axz and Ayy for the reaction H ( d , 2 p ) n are studied by kinematically overdetermined measurements at an incident energy of 16 MeV at collinear and somewhat off-collinear kinematic conditions. A three-body Faddeev model using two realistic separable potentials that have different short-range parts gives a good fit to the data. Uncertainties in Coulomb corrections make it difficult to draw definitive conclusions about possible three-nucleon force effects at collinearity conditions.

Two-spectator quasifree processes (graphs with two spectator particles) for the 3 He( 3 He, dd)pp reaction at the symmetric angle pairs θ = 30.1° at E 3 He = 50 MeV and θ = 37° at E 3 He = 78 MeV are investigated. The theoretical cross sections are calculated with the PWIA model. The measured cross sections are smaller but have shapes which are in good agreement with the calculation. The ratio N = experiment/theory is approximately 0.05 at 50 MeV and 0.1 at 78 MeV. The reaction 2 H(d, pp)nn also was studied at the symmetric angle pair θ = 34.8° and E 2 H = 34.7 MeV and the ratio is about 0.14.

Quasifree scattering and quasifree reaction processes have been examined in the 3 He+ 2 H → p+d+d, 3 He + 2 H → n+p+ 3 He and 3 He+ 2 H → p+p+t reactions. Beam energies of E d = 22.3 and 35 MeV and of E 3He = 30, 33.5, and 52.5 MeV were used. The experimental results are compared with PWIA calculations and Fourier transforms of the wave functions are extracted. The quasifree processes are described qualitatively by the PWIA, but some features cannot be described by either PWIA or DWIA.

The sputtering yield, joint polar and azimuthal angular distributions and the energy distribution of atoms sputtered from copper single crystals by 100 keV copper ions has been calculated as a function of crystal orientation using the cascade simulation code MARLOWE. The calculated yields and angular distributions are compared with experimental results for ions incident parallel to a close-packed axial channelling direction, parallel to a plane, and along a pseudo-random direction. Significant channeling effects are exhibited in both calculations and experiment. Strong peaking in the backscattered direction is calculated and observed for the axial irradiations alone. Primary range distributions and damage profiles are calculated for the three crystal orientations and compared with lattice damage measurements. The distributions of sputtered ions in both energy and angle are presented.

The4He(\(\vec d\),pα)n cross section, vector and tensor analyzing-power data with 12 and 17 MeV deuterons at kinematic conditions including proton-alpha quasifree scattering, neutron-alpha and proton-alpha final-state interactions, as well as collinearity, are compared with the predictions of the three-body model using different nucleon-alpha and neutron-proton forces. In general, better two-body potentials give a better fit to the data, except for the vector analyzing-power data. The roles of the impulse and multiple-scattering amplitudes are studied to understand the sensitivity to two-body potentials and to understand the reason for the successes and the failures of the model.

Quasifree scattering and quasifree reaction processes have been examined in ten 3 H + 3 He and 3 He + 3 He reactions with at least two of the three or more final state particles being charged. Beam energies of 50, 65 and 78 MeV were used. The experimental results are compared with PWIA predictions and Fourier transforms of the wave functions are extracted. The quasifree processes are described in a consistent, but qualitative, manner by the PWIA; distortion in the intial state appears to be the cause of the consistent deviation of the data from the PWIA predictions. Extracted values for the 3 H(d, 3 He)2n cross section are given.

Copper targets were implanted with 125 keV gold and tantalum ions at selected incident angles of the beam relative to the target normal to examine the effect of the incident angle on the sputtering yields, the dose retained in the modified layer, and the atomic surface fractions. Sputtered particles were collected on aluminum foils to measure the angular distribution of the sputtered particles and to determine the partial sputtering yields of the beam and target species. A 1.5 MeV xenon beam implanted markers into the copper targets to determine the average sputtering yield for the surface during the implantation. Theoretical predictions from a surface binding energy correction model were compared with the experimental results. Although the predictions from the model were not exact, the trends of the data were in agreement with the model. The measured total sputtering yield increases with increasing incident beam angle, and, correspondingly, the fluence retained decreases with incident beam angle.

The sputtering yield and the angular distribution of sputtered atoms have been measured as a function of copper-ion-beam orientation with respect to copper single-crystal targets. Alpha-particle channeling has been employed to measure the lattice damage induced during the sputtering experiments. The experimental results have been compared with results from the cascade simulation program MARLOWE. Both planar and axial channeling of incident ions have been shown to significantly reduce the sputtering yield relative to a psuedo-random irradiation direction. Channeling of the incident particles also increases the depth to which lattice damage is produced. Surface preparation is found to strongly influence the orientation effects, with mechanical polishing reducing the channeling of incident ions, relative to electropolishing.

The applicability of the particle induced x-ray emission (PIXE) in the determination of sputtering distributions and yields was studied. Sputtered particles were caught on foils for the 45 keV to 125 keV self sputtering of Fe, Ni, Cu, Ti, Mo and Au and for the 90 keV sputtering of both target and implanted particles of Ni+ + Cu, Cu+ + Ni, Ni+ + Fe, and As+ + Ag, and for the target particles of Ar+ + Au. Sputtered particles were collected in an ultra high vacuum (UHV) and in a poorer vacuum system with 99.99% pure Al catcher foils. PIXE data, the x-ray yields from 1 MeV proton and 2 MeV alpha particle beam bombardments, were used to determine the angular distribution of the sputtered products. The sputtering yield was calculated from the angular disbution data by integration over a hemisphere assuming azimuthal symmetry. The efficiency of the PIXE systems was calibrated with a standardized target such as 18 ?g/cm2 Fe on the same 99.99% Al foil material. The Al x-ray yield of the catcher foils provided a normalization of all data from a given catcher foil. For a number of samples studied, we have been able to compare the distribution and yields obtained with PIXE to those measured by the Rutherford backscattering (RBS) technique. Also separate RBS analysis of Xe markers in the sputtering targets provided yield values. Comparision of the PIXE and RBS results indicate that the PIXE sputtering distribution and yield measurements are comparable.

The cross section and the analyzing powers A y , A xx and A yy for the reaction 4 He( d , αp)n are studied with kinematically complete measurements at incident energies of 12 and 17 MeV. Spectral structures due to the final-state interactions and quasifree scattering are measured. A three-body model of the Faddeev type gives a satisfactory fit to the cross-section and A y data, but it fails to fit adequately the tensor analyzing-power data. The tensor analyzing powers in the breakup process should be sensitive to the input two-body force, and that sensitivity seems to be somewhat greater near the three-body 1 + resonance.

Surface barrier detectors can measure the characteristics of neutron fields and related light-ion fluxes (LIF). Some of us have shown that a photodiode, with a suitably chosen radiator, can measure fluences of monoenergetic neutrons and have studied the shapes of a few continuous neutron spectra. Others have used silicon detectors to measure the energy of neutrons from reactions. We have attempted to perfect a simple, compact and inexpensive single surface barrier detection system to measure both the intensities and approximate spectral shape of continuous neutron and LIFs. We have measured such fluxes for three known collimated and uncollimated neutron beams with two geometrical configurations and with at least two different thicknesses of CH2 and CD2 radiators. All neutron flux data were obtained with a Au shield in front of the detector; this was removed for LIF measurements. The known shapes of the impinging neutron beams were used to calculate the expected recoil-particle spectra and such predictions have been compared with the experimental data. Also, data have been obtained with telescopes, with carbon foil and thin detector-grade silicon foil radiators. These data allow us to estimate contributions to the higher-energy portion of the recoil-particle spectra from reactions due to the carbon in the CH2 and CD2 radiators and due to the silicon in the detector. Corrections for rim effects in the detector and multiple scattering in the radiator are calculable.

Self-ion sputtering yields were determined for copper, nickel, and aluminum at 60 keV, 90 keV, and 120 keV. The sputtering yields were determined by Rutherford backscattering measurements of the energy shifts of a deeply implanted xenon marker layer and by measuring the distribution and amount of sputtered material on a catcher foil using backscattering and particle induced X-ray emission. The effect of dose rate and net fluence on the yield were examined. Optical monitoring of the light intensity emitted by the sputtered particle confirmed no measurable change in the yield using self ion bombardment. The self-ion sputtering yields measured in this study are less than predicted by theory but are self consistent within experimental error independent of measurement technique. Additional measurement of self-ion sputtering yields in this energy range are needed for applications in materials modification.

A variety of analyzing powers for d + p breakup reactions initiated by polarized deuterons incident on protons have been measured at deuteron bombarding energies of 16 and 79 MeV. The results are compared with Faddeev calculations using both separable (at 16 and 79 MeV) and local (at 79 MeV) interactions. These calculations include nucleon-nucleon forces in the S, P and D states and the 3S1−3D1 tensor force.

In this paper the surface binding energy model proposed by Reynolds for a binary alloy has been extended to a ternary system. From this model extension the steady state atomic surface fractions were calculated for a ternary surface alloy to be prepared by ion implanting a binary alloy of known composition. These predictions were compared with the results of the subsequent ion implantation experiments. The total implantation process was monitored by the observation of light emitted through de-excitation processes from sputtered neutral atoms. The experimental results reported are for nickel-chromium alloy implanted with 90 keV copper and tantalum and were analyzed using Rutherford backscattering, particle induced X-ray emission, and Auger surface analysis. From these results the partial sputtering yield for each component, net sputtering yield and surface atomic fractions were determined, and then compared with the predicted values. The different analytical techniques show consistent agreement within experimental error and there is reasonable agreement between the experimental results and the predicted values.

The 7 Li (α, t) 8 Be (α) 4 He and 7 Li (α, α') 7 Li ∗ ( t ) 4 He reactions have been observed in a kinematically complete experiment with E α = 50 MeV, particle identification, and on-line computer coincidence electronics. Sequential decay through the ground, 2.9, 11.4, 16.6 and 16.9, and 19.9 MeV states of 8 Be and the 4.63 and 7.48 MeV states of 7 Li has been observed. Triton angular distributions for the decay through the ground state of 8 Be were obtained with and without coincidence requirements. Agreement of these distributions implies isotropic decay in the c.m. of the 8 Be ground state. The contribution of quasi-elastic processes is small due to the specific limited portion of phase space observed.

The external beam handling system consists of two 110 deg , n = 1/2 focusing magnets with radii of curvature 200 cm and three 180 deg , n = 1/2 analyzer magnets with radii of curvature of 133 cm. The energy resolution provided by the ion-optics is E/ DELTA E = 8 x 10/sup 3/. The design is based on first order theory, but second order equations were programmed for a 709 computer to study aberrations and the position of the focal surfaces in the three-magnet analysis system. The general properties of the magnets are described. (auth)

The quasielastic scattering of 50-MeV $\ensuremath{\alpha}$ particles has been used as a tool to study the cluster configurations of the $^{6}\mathrm{Li}$ nucleus by means of the $^{6}\mathrm{Li}(\ensuremath{\alpha},\ensuremath{\alpha}x)Y$ reaction. Data have been obtained in kinematically complete experiments and at exact quasielastic angles for those cases corresponding to $x=p, d, t$, He, and $\ensuremath{\alpha}$. Analysis has been carried out in the framework of the plane-wave impulse approximation. Quasielastic cross sections have been measured and experimental momentum distributions extracted. Theoretical fits to these distributions using simple Gaussian and exponential functions have been calculated and used to determine both absolute and relative clustering probabilities with fair success. The more reliable relative probabilities indicate strong $p, d$, and $\ensuremath{\alpha}$ clustering in $^{6}\mathrm{Li}$ and rather weak $t$ and $^{3}\mathrm{He}$ clustering.